Impregnated material and method of treating the same



Patented Aug. 28, 1928.

UNITED STATES I 1,682,652 PATENT OFFICE.

LYMAN I. WHITNEY, F BOSTON, AND WILLIAM E. WHITNEY, or NEWTON, MASSA- onUsnTTs, ASSIGNORS, BY MESNE ASSIGNMENTS, To RAJET COMPANY, or BOSTON, MASSACHUSETTS, A CORPORATION or M SSACHUSETTS.

IMPREGNATED MATERIAL AND METHOD OF TREATING THE SAME.

Ho Drawing.

This invention relates to the treatment of fibrous material, such as leather, with an impregnating solution, and more particularly a solution containing a cellulose derivative, as, for example, nitrated cotton, and consists in certain improvements in such treatment and in the productresulting therefrom.

The invention will be best understood from the following explanation of one mode or manner of practicing the improved process, While its scope will be more particularly pointed out in the appended claims.

In the following description we have taken as one specific illustration of the application of the process the impregnation of chrome tanned leather which, for example, may be intended for use as sole leather, but the process may have useful application in the impregnation of other classes of leather or material other than leather and intended for various uses.

Where material, such as chrome leather, is properly impregnated by immersion in a solution containing a cellulose derivative such, for example, as nitrated cotton or cellulose acetate, and the solution thereafter dried out, the leather acquires increased density, water resistance, durability and other wear resisting qualities. During the impregnation and (or) subsequent drying of the leather it tends to become dehydrated and the leather shrinks due to the loss of the moisture which, under standard atmospheric conditions, is contained within the fibres. This impregnated leather tends eventually to reabsorb the moisture and swell.

To prevent or reduce the shrinkage of the impregnated material, we introduce into the fibrous body of the material an anti-shrinking agent in the form of a substance that tends to swell or expand the fibres and will not be driven off in removing the nitrated cotton solvents from the cotton. Such substance may be introduced into the fibres prior to impregnation, or, if capable of being mixed with the impregnating solution, it may be introduced during impregnation.

Anti-shrinking agents may be employed in the form of high boiling, hydroscopic materials such as glycerine, trimethelene glycol or ethyl urea. In the case of the impregnation of chrome leather we have found that a certain proportion of glycerine mixed with Application filed January 15, 1924. Serial No. 686,464.

a nitrated cotton solution may be employed to impregnate the leather (the glycerine probably acting upon the fibres) so as to prevent in a large measure that shrinka e which would otherwise result from ehydration, either through impregnation or through the removal of the nitrated cotton solvents. Glycerine also serves to soften or render more flexible the leather and thus serves the purpose for which castor oil or other non-drying oils have been employed in this connection.

Where substances such as glycerine and castor oil or other non-drying, non-solvent oils are employed (for the purpose of softening the impregnated material or for other purposes) in connection with nitrated cotton solutions employing the ordinary low boilmg solvents, in the course of drying the solvents out of the material after impregnation, a concentration of the cotton solution is apt to be reached Where some of the cotton precipitates, resulting in a less efficient film or impregnating body for the fibres of the impregnated material. WVe have found that this tendency may be counteracted in whole or in large measure by adding to the cotton solution an amount of high boiling solvent which tends to keep the cotton sufliciently in solution after the low boiling solvents have evaporated, thereby preventing the tendency of the cotton to precipitate and yet providing a strong and flexible impregnating body. Thus, by adding to the cotton-glym erine solution a certain amount of high boiling solvent or gelatinizing agent, such as diethyl phthalate, an impregnating body is produced which gives better results than a similar solution without the diethyl phthalate. Other high boiling solvents and gelatinizing agents may be used such as triphenal phosphate, ethyl urea, camphor or triacetin.

As the solvents undergo evaporation after impregnation and the nitrocellulose solution hardens, the impregating coating for the fibres tends to shrink more or less. This tends to produce minute shrinkage holes between the fibres which lessens the water resisting qualities of the impregnated material. lVe have found that, by adding'to the cotton solution a material, solid at ordinary temperatures but fluid at the temperature at which the cotton solution is used, and

capable of being mixed with or dispersed in the cotton solution, it is possible to obtain an impregnated material which has increased imporosity and water resisting qualities. It is preferable that such material have a specific gravity approaching that of the cotton solution. A cotton film combined with a filler of this type presents characteristics which are different from a film without such filler. We. have found that when chrome leather is impregnated with a nitrocellulose solution and paraffin it retains the paraffin at a temperature in excess of the temperature at which such paraffin would melt out of the leather in the absence of the cotton film. Suchfilling material may be selected from a broad range of substances. We have found, for example, that waxes such as paraffin, carnauba wax and halowax are suitable for this purpose. Resinous materials such as cumar, and fatty acids such as stearic acid, can be used to advantage. But these are only a few of the great number and classes of substances that can be adapted to this purpose.

As illustrative of our improved process, the following is submitted as one mode or manner of practicing the same, wherein the impregnation of chrome tanned leather is effected. This may be carried out by first preparing an impregnating solution containing a cellulose derivative, such, for example, as nitrated cotton and cellulose acetate. We prefer to employ nitrated cotton dissolved in a low boiling solvent, such as a mixture of methyl acetone and wood alcohol, although there may be used for the solvent such substances as a mixture of methyl acetone and ethyl alcohol, ether, ethyl acetate or methyl acetone. Where cellulose acetate is employcd the low boiling solvent might consist of tetrachlorethane. \Ve have found that a mixture comprising principally methyl acetone and wood alcohol, marketed under the trade name of Kolin, gives satisfactory results with nitrated cotton. To this solution there is preferably added certain amounts of parafiin wax, stearic acid, glycerine and a small quantity of high boiling solvent such as diet iyl phthalate. It will be understood that some of these substances may be omitted, and that for some of them others may be substituted capable of effecting in greater or less measure the desired objects, the described solution being submitted mcrely as a single illustrative example.

The proportions may be more or less varied, but as illustrative of suitable proportions these substances may be employed in the proportion of 2.5 pounds of cotton, 7.4 pounds of Kolin, .6 pounds of paraffin, .6 pounds of stearic acid, 1.5 pounds of glycerme, and .25 pounds of diethyl phthalate.

The impregnating solution thus prepared 15 then preferably placed in a closed or pressure-tight container and therein subjected to a temperature of from 125 F. to 135 F. for from ten to twenty-four hours, the mixture being agitated either continuously or from time to time. as by the rotation of the. container in suitable bearings.

\Ve have found that the viscosity of mtrated cotton solution becomes substantially less with increase of tem 'ierature, and this effect is particularly marked when the solution is kept under the pressure of its own vapor in a closed container. This increases the impregnating efficiency of the solution in that it permits a highly concentrated solution to be used while having a permeating effect on the material of a solution of lower concentration.

The mixture having been treated as above described, it is then preferably cooled to about 80 F., the container opened and the leather introduced into the container, care being taken that the surface of the leather is entirely immersed and covered by the mixture.

The container containing the mixture and the leather is then again made pressure tight and rotated on its bearings so that its peripheral velocity is about 5 feet per second. The temperature is then raised to between 130 F. and 140 F. and there maintained while the container is subjected to rotation, either continuous or intermittent, until impregnation is complete.

The container is then cooled to about 80 F. and opened, the leather removed and its surface freed from any of the adherent mixture, after which it is preferably subjected to heat and pressure. For this purpose the leather may be dried in an oven at a temperature from 100 F. to 120 F. for from two to five hours, depending on its thickness, and thereafter subjected for from three to four minutes to a pressure of about 500 pounds to the square inch between surfaces heated to about 120 F. to 130 F. Preferably the leather is thereafter dried in an oven at a temperature of from 100 F. to 120 F. for several days, after which it is ready for use.

While we have herein described one illustrative example of our improved product and the several steps by which one specific form of the process may be carried out, it is to be understood that our invention is not limited to the ingredients, proportions or exact details specified, but that these may be varied within wide limits, and various other applications of the process may be made, without exceeding the true scope of the invention which is more definitely set forth in the following claims.

Claims.

1. A new article of manufacture com rising chrome leather impregnated with nitrocellulose and glycerine.

2. As a new article of manufacture, leather impregnated with a cellulose derivative and an anti-shrinking agent.

8. As a new article of manufacture, leather impregnated with a cellulose derivative and ananti-shrinking agent, the latter comprising an anti-shrinking substance -capable of resisting a drying heat.

4. As a new article of manufacture, leather impregnated with a cellulose derivative and a high boiling hydroscopic material.

5. As a new article of manufacture, leather impregnated with an anti-shrinking material, a cellulose derivative and a high boiling solvent.

6. As a new article of manufacture, leather impregnated with nitro-cellulose and dicthyl phthalatc.

7. The method of producing an impregnated leather which consists 1n immersing the leather in an impregnating solution con-- taining'a cellulose derivative, evaporating the solvents, and introducing an anti-shrinking substance prior to such evaporation.

8. The method of producing an impregnated leather which consists in impregnating chrome leather with glycerine and also with a solution containing a cellulose derivative and drying the impregnated leather.

9. The method of producing an impregnated leather which consists in impregnating the leather with a cotton solution which contains a relatively low boiling cotton solvent, a relatively high boiling cotton solvent and glycerine, and drying the impregnated leather.

10. Themethod of impregnating leather which consists in' subjecting it to the im pregnating action of a heated solution containing a cellulose derivative, introducing into the body of the leather a filler solid at ordinary temperatures but fluid at the impregnating temperature, evaporating the solvents, and introducing an anti-shrinking substance prior to such evaporation.

11. As a new article of manufacture, leather impregnated with nitro-cellulose and a high boiling solvent.

In testimony whereof, we have signed our names to this specification.

LYMAN. F. WHITNEY. WILLIAM E. WHITNEY. 

